Ctenosaura defensor (Cope, 1866). The Yucatecan Spiny-tailed Iguana, a regional endemic in the Mexican Yucatan Peninsula, is distributed in the Tabascan Plains and Marshes, Karstic Hills and Plains of Campeche, and Yucatecan Karstic Plains regions in the states of Campeche, Quintana Roo, and Yucatán (Lee, 1996; Calderón-Mandujano and Mora-Tembre, 2004), at elevations from near “sea level to 100 m” (Köhler, 2008). In the original description by Cope (1866), the type locality was given as “Yucatán,” but Smith and Taylor (1950: 352) restricted it to “Chichén Itzá, Yucatán, Mexico.” This lizard has been reported to live on trees with hollow limbs, into which they retreat when approached (Lee, 1996), and individuals also can be found in holes in limestone rocks (Köhler, 2002). Lee (1996: 204) indicated that this species lives “mainly in the xeric thorn forests of the northwestern portion of the Yucatán Peninsula, although they are also found in the tropical evergreen forests of northern Campeche.” This colorful individual was found in low thorn forest 5 km N of Sinanché, in the municipality of Sinanché, in northern coastal Yucatán. Wilson et al. (2013a) determined its EVS as 15, placing it in the lower portion of the high vulnerability category. Its conservation status has been assessed as Vulnerable by the IUCN, and as endangered (P) by SEMARNAT. ' © Javier A. Ortiz-Medina 263 www.mesoamericanherpetology.com www.eaglemountainpublishing.com The Herpetofauna of the Mexican Yucatan Peninsula: composition, distribution, and conservation status VÍCTOR HUGO GONZÁLEZ-SÁNCHEZ1, JERRY D. JOHNSON2, ELÍ GARCÍA-PADILLA3, VICENTE MATA-SILVA2, DOMINIC L. DESANTIS2, AND LARRY DAVID WILSON4 1El Colegio de la Frontera Sur (ECOSUR), Chetumal, Quintana Roo, Mexico. E-mail: [email protected] 2Department of Biological Sciences, The University of Texas at El Paso, El Paso, Texas 79968-0500, United States. E-mail: [email protected], [email protected], and [email protected] 3Oaxaca de Juárez, Oaxaca 68023, Mexico. E-mail: [email protected] 4Centro Zamorano de Biodiversidad, Escuela Agrícola Panamericana Zamorano, Departamento de Francisco Morazán, Honduras. E-mail: [email protected] ABSTRACT: The herpetofauna of the Mexican Yucatan Peninsula is comprised of 145 species, including 22 anurans, three salamanders, two crocodylians, 102 squamates, and 16 turtles. We examined the state-level distribution of the herpetofauna of this region, which revealed that the largest number of amphibian spe- cies (24 of 25) is recorded for Campeche, followed by Quintana Roo (22), and then by Yucatán (17). The largest number of crocodylians, squamates, and turtles is reported for Quintana Roo (107 of 120), with the next highest number in Campeche (104) and then in Yucatán (88). We documented the distribution of the herpetofauna among the six physiographic regions recognized herein, including four mainland regions and two insular ones. The total number of species in these six regions ranges from 43 in the Gulf Islands region to 120 in the Karstic Hills and Plains of Campeche. The individual species inhabit from one to six regions (x– = 3.7). The largest number of single-region species (five) is restricted to the Yucatecan Karstic Plains. We constructed a Coefficient of Biogeographic Resemblance (CBR) matrix that demonstrates the number of shared species ranging from 26 between the Caribbean Islands and Gulf Islands to 104 between the Karstic Hills and Plains of Campeche and the Yucatecan Karstic Plains. The CBR values range from 0.44 between the Karstic Hills and Plains of Campeche and the Caribbean Islands to 0.88 between the Gulf Islands and the Karstic Hills and Plains of Campeche. Based on the CBR data we constructed an Unweighted Pair Group Method with Arithmetic mean (UPGMA) dendrogram, which indicates that the four mainland physiographic regions are fairly closely related to one another because they share a sizable number of broadly distributed species, and are fairly distantly related to the two insular groupings perhaps because of the dispersal ability bias seen among members of the mainland herpetofauna. Only about 24% of the herpetofauna is distributed in one or two of the six regions, demonstrating the relatively broad dis- tribution of many species on the peninsula. We placed the members of the herpetofauna into four distribu- tional categories, of which the largest number (127 of 145) is allocated to the non-endemic category; rela- tively small numbers are placed in the regional endemic category (11), followed by the non-native species (six) and the country endemic category (one). We identified the principal environmental threats as agri- culture and deforestation, hurricanes and other tropical storms, forest fires, tourist development, infectious diseases, invasive species, climate change, illegal collecting, oil mining, killing on roads, and other forms Mesoamerican Herpetology 264 June 2017 | Volume 4 | Number 2 González-Sánchez et al. Herpetofauna of the Mexican Yucatan Peninsula of direct and incidental killing. We assessed the conservation status of the native species by employing the SEMARNAT (NOM-059), IUCN, and Environmental Vulnerability Score (EVS) systems, of which the EVS proved to be the most useful. The number of species in the three EVS categories decreased from low (57) through medium (51) to high (26). We also used the EVS rankings to determine how species in the IUCN Not Evaluated (NE) and Least Concern (LC) categories might be evaluated more informatively. In addition, we used a means of determining Relative Herpetofaunal Priority (RHP), a simple method for ascertaining the rank order of a physiographic regional herpetofauna based on the number of peninsular and national endemic species, as well as the number of high vulnerability EVS species. Using these mea- sures, we concluded that the Yucatecan Karstic Plains ranked as the highest priority region, in both cases. Moreover, we discuss the capability of the protected areas of the Mexican Yucatan Peninsula to provide protection for members of the herpetofauna. Based on our analysis, we erected a set of conclusions and recommendation for the perpetual protection of the peninsular herpetofauna. Key Words: Anurans, caudates, physiographic regions, protected areas, protection recommendations, squamates, turtles RESUMEN: La herpetofauna de la Península de Yucatán mexicana consiste de 145 especies, incluyendo 22 anuros, tres salamandras, dos cocodrílidos, 102 escamosos y 16 tortugas. Examinamos la distribución de la herpetofauna a nivel estatal, la cual reveló que el mayor número de anfibios (24 de 25) se encuentra en Campeche, seguido por Quintana Roo (22) y Yucatán (17). El mayor número de cocodrílidos, escamosos y tortugas está reportado en Quintana Roo (107 de 120), seguido por Campeche (104) y después por Yucatán (88). Documentamos la distribución de la herpetofauna entre las seis regiones fisiográficas aquí recono- cidas, incluyendo cuatro regiones continentales y dos insulares. El número total de especies en estas seis regiones va de 43 en la región de las Islas del Golfo, a 120 en Carso y Lomeríos de Campeche. Las espe- cies ocupan de una a seis regiones (x– = 3.7). El número más grande de especies que se encuentran en una sola región (cinco) está restringido a la región Carso Yucateco. Construimos una matriz de Coeficientes de Similitud Biogeográfica (CBR) que demuestra que el número de especies compartidas va de 26 entre las Islas del Caribe y las Islas del Golfo a 104 entre Carso y Lomeríos de Campeche y Carso Yucateco. Los valores de CBR van de 0.44 entre Carso y Lomeríos de Campeche y las Islas del Caribe a 0.88 entre las Islas del Golfo y Carso y Lomeríos de Campeche. De acuerdo con los datos del CBR, construimos un dendrograma basado en el método de UPGMA, el cual indica que las cuatro regiones fisiográficas en tierra firme están estrechamente relacionadas porque comparten un número significativo de especies con amplia distribución, y están distantemente relacionadas con los dos grupos insulares, probablemente debido a la capacidad sesgada de dispersión entre miembros de la herpetofauna en tierra firme. Solamente alrededor del 24% están distribuidas en una o dos de las seis regiones, demostrando la relativamente amplia distri- bución de muchas especies en la península. Ubicamos a los miembros de la herpetofauna en cuatro cate- gorías de distribución, de los cuales el número más grande (127 de 145) está asignado a la categoría de es- pecies no endémicas; números relativamente menores están ubicados en la categoría de endémicas a nivel regional (11), seguidos por las especies no nativas (seis) y las endémicas al país (una). Identificamos las amenazas ambientales principales como la agricultura y deforestación, huracanes y tormentas tropicales, incendios forestales, desarrollo turístico, enfermedades infecciosas, especies invasoras, cambio climático global, colección ilegal, actividad petrolera, muerte por atropellamiento, y otras formas de eliminación directa o indirecta. Estimamos el estatus de conservación de las especies nativas empleando los sistemas de SEMARNAT (NOM-059), IUCN, y Valor de Vulnerabilidad Ambiental (EVS), de los cuales el sistema de EVS mostro ser más útil. El número de especies en las tres categorías de EVS disminuyó de la baja (57), media (51) a la alta categoría (26). También usamos los rangos del sistema de EVS para determinar cómo las especies en las categorías de No Evaluadas (NE) y de Preocupación Menor (Least Concern [LC]) de la UICN